Expansible anchor and method of making same

Abstract

The expansible anchor consists of a shank having a threaded portion for fixing an article at its rear end and a reduced cross-sectioned portion with an adjoining expander cone at its front end, and, positioned over the reduced cross-sectioned portion, an expansible sleeve having longitudinal slits forming expansible segments and locking elements protruding beyond the diameter of the expansible sleeve and arranged on the expansible segments. To increase the holding force of the anchor and to allow the expander cone to slide-up and the expansible sleeve to expand in operation if the drilled hole become enlarged as a result of cracks forming, the locking elements consist of several interconnected punched elements on each expansible segment extending in a longitudinal direction of the expansible segments. Each punched element is triangular with a point directed towards the front end of the expansible segments. An improved method of making the expansible anchor which includes stamping a blank for the expansible sleeve somewhat undersized from sheet metal, subsequently pressing it and then punching the punched elements in the expansible sleeve is also described.

We claim: 
     
       1. An expansible anchor for anchoring in a hole drilled in a concrete part, said expansible anchor consisting of a shank having means for fixing an article at a rear end of said shank, a reduced cross-section portion having a reduced cross section and an expander cone at a front end of said shank and adjoining said reduced cross-section portion, and, positioned over the reduced cross-section portion of the shank, an expansible sleeve provided with a plurality of longitudinal slits forming expansible segments in said expansible sleeve and having locking elements protruding beyond a diameter of the expansible sleeve and provide on the expansible segments; and wherein the locking elements comprise at least one plurality of punched elements extending in a longitudinal direction of the expansible segments which punched elements are interconnected so as to eliminate distances between said punched elements and therefore avoid formation of weak points between said punched elements, each of the punched elements being triangular in shape and having a tip directed towards a front end of the expansible segments. 
     
     
       2. An expansible anchor according to claim 1, wherein four of said interconnected punched elements are provided on each of said expansible segments, and said four interconnected punched elements have an overall length equal to about half a total length of said expansible sleeve and a maximum width equal to approximately one third of a width of one expansible segment. 
     
     
       3. An expansible anchor according to claim 1, wherein a height of each of said punched elements corresponds approximately to a third of a wall thickness of the expansible sleeve and each of said punched elements has a tip and is inclined inwardly towards said tip. 
     
     
       4. An expansible anchor according to claim 1, wherein said expansible segments have longitudinal sides provided with a plurality of opposing indentations. 
     
     
       5. An expansible anchor according to claim 1, wherein the expansible sleeve has an inner front edge provided with a bevel for engagement with the expander cone. 
     
     
       6. An expansible anchor according to claim 1, wherein said expansible segments have rounded front corner edges. 
     
     
       7. An expansible anchor according to claim 1, wherein each of said expansible segments is provided with one of said pluralities of said punched elements. 
     
     
       8. An expansible anchor according to claim 7, wherein four of said punched elements are provided on each of said expansible segments, and said four punched elements have an overall length equal to about half a total length of said expansible sleeve and a maximum width equal to approximately one third of a width of one expansible segment. 
     
     
       9. A method of making an expansible anchor consisting of a shank having means for fixing an article are a rear end thereof, a reduced cross-section portion and an expander cone at a front end thereof, said reduced cross-section portion adjoining said reduced cross-section portion, and, positioned over the reduced cross-section portion of the shank, an expansible sleeve provided with a plurality of longitudinal slits forming expansible segments therein and having at least one set of punched elements which punched elements are interconnected so as to eliminate distances between said punched elements and therefore avoid formation of weak points between said punched elements, said punched elements protruding beyond a diameter of the expansible sleeve and provided on the expansible segments, said method comprising the steps of: a) stamping a blank from sheet metal for the expansible sleeve slightly undersized in relation to the expansible sleeve;   b) pressing the blank to reduce a sheet metal thickness of the blank and to simultaneously increase hardness and surface smoothness of the blank; and   c) after pressing, punching the interlocked punched elements in the blank.   
     
     
       10. Method according to claim 9, further comprising, after the punching of the interlocked punched elements, bending the expansible sleeve into a U-shape for engagement with said reduced cross-sectioned portion.